This application is based upon and claims priority from prior French Patent Application No. 01-00818, filed Jan. 22, 2001, the disclosure of which is hereby incorporated by reference in its entirety.
1. Field of the Invention
The present invention generally relates to semiconductor devices and more particularly to integrated circuits, in which windings constituting inductors, in particular magnetically-coupled inductors, are made so as to constitute a transformer.
2. Description of Related Art
The production of a transformer comprising a spiral primary metal winding and a spiral secondary metal winding made in the same layer with the turns of the winding wound in parallel is known in the art. The production of a transformer with different outputs in two spiral secondary metal windings formed in the same layer with the inner ends of these two windings being connected by vertical vias, is also known in the art. Such a topography is known by the name xe2x80x9cbalun.xe2x80x9d Such transformers are described in document 1998 IEEE, page 105.
Although the production of the transformer is useful, it is not without its shortcomings. One shortcoming is there is no way to supply two signals of equal amplitude. Another shortcoming is there is no way to supply two signals of equal magnitude but with a phase of 180xc2x0. Accordingly, there is a need to overcome these shortcomings and to provide a transformer that supplies two signals of equal magnitude but with a phase of 180xc2x0.
The present invention provides a semiconductor device with an integrated circuit formed over several levels and made in several layers. The integrated circuit includes a metal circuit capable of constituting two secondary inductors and a primary inductor, the geometry of which makes it possible, when it is magnetically coupled to this primary inductor, to supply two signals of equal amplitude but with a phase difference of 180xc2x0.
According to the invention, the device comprises a metal circuit comprising two parts wound into a spiral which have inner ends and outer ends between which they comprise branches which lie on either side of a median longitudinal region and the successive branches of which are connected by intermediate junctions crossing this median longitudinal region.
According to the invention, the parts wound into spirals are formed such that the branches of one of the parts and the corresponding branches of the other part, lying on either side of the median longitudinal region, are made in the same level and are symmetrical with respect to this median longitudinal region, that a common junction connects the inner ends of the parts and lies across the median longitudinal region, and that the intermediate junctions between the branches of one of the parts passes above or below the intermediate junctions between the branches of the other part.
According to the invention, the device comprises a common external connection means connected to the common junction and separate external connection means connected respectively to the outer ends.
Thus, the wound parts of the metal circuit constitute two secondary metal windings which are symmetrical and formed between the common connection means and the separate connection means, respectively, and constituting symmetrical inductors.
According to the invention, the primary winding comprises two parts wound into spirals which have inner ends and outer ends between which they comprise branches which lie on either side of a median longitudinal region and the successive branches of which are connected by intermediate junctions crossing this median longitudinal region.
According to the invention, the parts wound into a spiral are formed such that the branches of one of the parts and the corresponding branches of the other part, lying on either side of the median longitudinal region, are made in the same level and are symmetrical with respect to this median longitudinal region, that a common junction connects the inner ends of the parts and lies across the median longitudinal region, and that the intermediate junctions between the branches of one of the parts passes above or below the intermediate junctions between the branches of the other part.
According to the invention, the primary circuit comprises separate external connection means connected respectively to the outer ends.
According to the invention, the branches of the wound parts are U-shaped.
According to the invention, the outer ends of the wound parts are placed adjacently.
According to the invention, the intermediate junctions which cross are preferably such that one is in the level of the corresponding wound part and that the other consists of a bridge having a branch in another level and vias for connecting to the branches of the corresponding wound part.
According to the invention, the separate connection means are preferably symmetrical with respect to the median longitudinal region and the common connection means lies along this median longitudinal region.
According to the invention, the connection means preferably comprise branches which lie parallel to the median longitudinal region, the separate connection branches of the parts being made at the same level as these parts and the common connection branch being made at a level other than these parts and than the intermediate junctions and being connected to the common junction by vias.
According to the invention, the device preferably comprises an electrostatic screen which lies below the metal circuit.